The invention relates to a tubular electric incandescent lamp provided with:
a tubular translucent lamp vessel which is sealed in a vacuum-tight manner and has a longitudinal axis,
a filament longitudinally arranged in the lamp vessel,
a respective metal hood arranged in a respective cup-shaped insulator housing secured to the ends of the lamp vessel,
current supply conductors extending from the filament to a respective metal hood,
contact members which are connected to a respective metal hood and extend through an opening in the respective insulator housing to the exterior transversely with respect to the longitudinal axis of the lamp vessel.
Such a lamp is known from U.S. Pat. No. 2,145,787.
The known lamp has disk-shaped metal hoods which are fused with the tubular lamp vessel. The metal hoods have in their central part a recess. The contact members are each undetachably connected to an insulator housing. They have at a part located within the insulator housing resilient fingers arranged so that they can together engage into the recess of a metal hood. The contact members are then rotatable through an arbitrary angle about the axis of the lamp vessel. A lamp provided at both ends with such a contact member is ready to be arranged with these contact members in the lamp holders of a luminaire intended to be used for this purpose.
The known lamp has the disadvantage that, when the lamp is removed from the luminaire, the connection between a contact member and the lamp vessel can be lost, while the connection between the luminaire and the contact member is maintained. If attemps are then made to remove this contact member from the luminaire, there is a risk that the resilient fingers are touched while they are still at a high voltage.
Since both contact members have to contact a respective lamp holder of a luminaire, the relative distance of these lamp holders should be adapted to the relative distance of the contact members. However, it has been found that the relative distance of the lamp holders can differ so greatly from the relative distance of the contact members of the lamp that the contact members must be given an oblique position respect to the axis of the lamp vessel in order to be able to arrange these contact members in the lamp holders. There may then be a risk that the resilient fingers of the contact members lose their grip on the recess in the metal hood. There may also be a risk that a metal hood of the lamp can be touched while the lamp is situated in the luminaire and is at a high voltage.
The invention has for its object to provide a lamp of a simple construction, whose contact members are undetachably connected to the metal hoods. The invention has more particularly for its object to provide a lamp having a construction which permits of using the lamp in luminaires having different lamp holder distances without another position of the contact members with respect to the longitudinal axis being required.